Mount: Four Thirds Construction: 18 elements in 13 groups, seven diaphragm blades Closest focus distance: 85cm Filter thread: 58mm Autofocus: stepping motor Dimensions: 67 x 100mm, 360g Tested on: Panasonic GX7
Thanks to the small image circle required by the Micro Four Thirds system, this 35-100mm lens is compact, yet gives the same effective zoom range as a 70-200mm lens on a full-frame body. Measuring 67 x 100mm, it's about half the length of similar lenses from Canon and Nikon, and under half the weight at just 360g. Despite a smaller filter thread of 58mm, it has a constant f/2.8 maximum aperture. This pays dividends in enabling fast shutter speeds in low light. The other advantage of constant-aperture zooms is that the full range of aperture settings is available at all focal lengths.
Build quality feels solid and includes dust and splash resistance, while the stepping motor autofocus system is typically silent. Manual focus relies on an electronic connection to the focus ring, rather than a physical coupling, but it's precise and smooth.
Panasonic's Power OIS (Optical Image Stabiliser) is also good to have, giving a benefit of about three stops in our tests and performing nearly as well as the stabilisers in telephoto zooms from other makers.
Sharpness is good rather than great at medium apertures, but the lens holds sharpness well at its widest f/2.8 aperture, and throughout the entire zoom range. Panasonic's Nano Surface Coating minimises ghosting and flare. Autofocus isn't quite as quick as in the ring-type ultrasonic lenses, but it's not far behind.
Sharpness: It's a fairly close match for other lenses in this zoom range, although the Panasonic fares better at its mid-range zoom setting.
Fringing: Colour fringing is slightly more noticeable compared to other telephoto lenses in this zoom range, but it's certainly not the worst.
Distortion: There's slight barrel distortion at every focal length, but it does decrease steadily as you zoom towards 100mm.
Verdict: Outright levels of sharpness aren't terrific, but at least the Panasonic delivers remarkable consistency throughout its whole zoom range.